Substituted Pyrrolidines not Derived from Proline

The use of various 2-substituted pyrrolidines directly deriving from (S)-pro-line was discussed in Chapter 9. Here, other 2-substituted pyrrolidines not directly deriving from the (5 )-proline scaffold will be further examined and analysed. 

Recently, Mayr and coworkers examined in detail the reactivity of catalysts (S )-34 and (S)-35d, comparing them to the Jorgensen-Hayashi-silylated (5)-a,a-diphenyl-prolinol 3a. While X-ray structures of the enamines deriving from (S)-34 and (S )-35d confirmed an almost perfect planarity of the enamine nitrogen, the high reactivity of catalyst (5)-35d was found to be due to a hyperconjugative interaction of ac si with 7i cn) increasing its Lewis basicity.  

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